Hi Reg
A couple of thoughts, that may only confuse - apologies in advance if they do!
First of all I like the sense of solidity for such a flat plate. I admit I usually try to go fairly thin - actually achieved a transparency once that beggared belief! - but whilst a thinner look seems better for more bowl like dishes I reckon a chunkier look for a flat dish/plate has its charms simply through being not-thin. And my ultimate critic thinks so to - which is nice! Cos I have several with similar proportions!!
And the little grooves work well too. You'll have seen I expect that they have a 'lightening' effect. Nicely done - that's something I'm still very much experimenting with - which of course is turner-talk for I've made quite a lot of grooved firewood whilst I've been experimenting!
Practice will bring the thinner/slimmer styles along as your confidence grows.
Pete can tell you all about vanishing bottoms in turned projects!
IMHO there are two main likely reasons for those seeming gouge marks, both already identified, and that's either not maintaining a steady pressure for the cut - especially for the last couple of finishing ones - which allows the bevel to bounce in and out of cutting/burnishing mode, or there's been a bit of wood movement (I was going to say 'bow(e)l movement' - ha ha, but that would be rude!).
Each of these likely reasons has one or more factors to consider (sometimes I find turning makes the brain hurt!!).
Tool sharpness may be a contributory reason, but the rest of your work looks well-cut to me, so I'm not so sure!
Steady cutting pressure - lack of - possible causes........
(these are all easy to say, but much much harder to get right!)
1 - simply not maintaining a consistent pressure, often a too short cutting stroke/movement - easy cure, practice practice and more practice - you'll learn to feel it 'being right', or 'not right', as the case may be! Soft wood is good for this practice cos it shows abuse marks more easily than hardwood - you've probably already found that it can be more difficult to turn a good finish on softwoods rather than hardwoods. They tear and bruise easily.
2 - as for 1, but down to posture - usually over-extending/stretching out as the finishing part/area of the cut is further away from you, so you're not in control - cure is to think posture and maintain a constant distance from the cutting action whenever possible, swing/swivel the hips!
3 - allowing the gouge to roll away from the line of cut as it cuts, so the shape of the cut changes as you present different parts of the cutting edge to the wood - think skidding round a bend in a car, and how the shape of four wheel contact and the forward car motion alter (and the sideways and backward motions too!!) - you probably realise the change in cutting pattern has happened and the automatic response is to push harder, which cuts deeper, so you ease off, and the circle has begun!!!...... all good cause and effect stuff isn't it?!
Ok, that's enough for the 'steady pressure' thing, now for 'wood movement'..........
1 - that the wood is moving 'out of true' as it turns - can happen if you're holding the piece with light pressure, or if the holes have become larger as you've worked it. In other words it's been having a bit of a wobble! Doesn't need to be much to effectively change the 'definition' of the circle that you are shaping, which could cause those marks.
2 - (not really wood movement this one, but I promise it is v v v common!) that you're not maintaining contact with the tool rest, so the chisel has the chance to 'bounce', and then 'digs' a bit as you recover and settle in again. Each time you 'hit' the wood as the chisel bounces.
And the cure is pretty much same as always - you know what I'm going to say! Practice, etc., etc.
I can also only echo the advice above to go watch a pro, several if you get the chance (we're talking cat-skinning techniques here!! There's always at least two ways to do something, and that doesn't include the wrong way! But the ground 'rules'/techniques are always the same. And they are what you need to be using.) - and think very carefully about what he/she achieves and how they're doing it.
A lesson would be a cracking investment now too.
Self-taught is probably the way into turning for most folk, but it's like most skills - if we don't fully appreciate the 'rules' we can't really begin to understand how/why method 'a' produces consistently good results, whilst method 'b' produces mostly firewood!