Hi Fiona and welcome to The Tortoise Table. He's a lovely little Hermann's tortoise (what is his name?). Yes, it does look like he is developing some pyramiding. There are several causes of this, for example eating the wrong kinds of food (particularly food that is high in protein), eating too much of the right kind of food (tortoises come from areas where food is often scarce so in the wild they eat far less than we offer them in captivity), and sometimes humidity issues (too dry and environment can sometimes contribute).
The main cause is usually eating too much, so for that reason we monitor their weight and restrict or enhance the diet accordingly. What you want to aim for is a weight gain on average of between 1g - 3g per month. This is just an average and some months he will gain more and some less, but it's a guideline.
The diet you are giving him is OK, but not ideal, to be honest. I would cut out the fruit altogether. The digestive system of tortoises doesn't cope well with the natural sugars in fruit, and although it won't kill him, it can upset his digestive system and really isn't necessary (that won't have contributed to pyramiding though). Also, lettuce is OK for hydration as it has a lot of water in it, but is not very nutritious, and is what we call a 'wet food', which means that it goes through their digestive system very quickly and they don't absorb many nutrients. If you have a look at the database on our website you can find lots of good plants that grow in your garden, in the wild and in your house to feed him. We have a traffic light system for feeding (green, amber-green, amber-red and red) and that is all explained in the How to Use section of the website. You can look up any plant and see if it is good for him, and you can also filter the whole database to show only good plants to feed.
https://www.thetortoisetable.org.uk/ If you want guidance on how to do this just let me know.
If you carefully monitor his weight gain and feed a good diet his current pyramiding won't disappear but this future growth will be smooth and in a few years time the little pyramid bumps won't be noticeable at all. You probably already have one, but in case you don't, here is a link to a care sheet for Hermanns:
https://www.tortoise-protection-group.o ... 014New.pdf
Just one other question. You mention the 100W solar basking spotlight. Is this a light that provides UVB as well as light and heat? UVB is really important in the development of shell and bone and the lights need changing every year or two, so if his UVB is inadequate that could be causing shell problems too.
It is great that you are bathing him often, as that is very important too. Is he in a tortoise table or a vivarium (if you could post a picture of his set-up that would be great).
I think you are providing him with a good home, and it is great that he has access to the outside when the weather is good (the sun is the best provider of UVB light), so I think your care just needs a few tiny tweaks and it will be perfect!
Nina