Is my bearded dragon too small

Ive had my bearded dragon since October now and he was around 12 inches then but its now February and he has only grown about 1 and a half inches and shedded once, should i be concerned? Im unsure of his age however if i had to guess he would be around 10 months currently he is nearly 14 inches and weighs about 258 grams. In October he was 150 grams so he is gaining weight. I feed him around 40-50 feeders a day including crickets, calci worms and sometimes Dubai roaches. However hes kinda eating more veg now such as rocket and caollard greens which i know is normal. His baking temps are around 38-41 degrees Celsius and a UVB 10.0 tube. A 4ft by 2 by 1 ft wooden virarnuim and a lino substrate. I mist him 3 to 4 times a day and bathe him about 2-4 times a week. He was sick for about a month during winter however has recovered now.

They grow in spurts so he may still have a few more spurts to go. As long as he is active and is eating readily (the amount will also vary over time) then I wouldn't worry about it too much. Can you post some photos of him? You can upload photos here https://www.beardeddragon.org/useruploads/ and post them to your thread using the XIMG button.

At 10 months old my mob were the followings weights
Puff (M) = 311.5g
Rex (F) = 329.5g
Peppa (F) = 382.4g
Toothless (M) = 341.2g

Peppa and Toothless raised identically (almost to the bug) , similar with Puff and Rex. You will see there is a range in sizes at the same age. While your's is a bit smaller, I know one at least of Rex and Puff's siblings was about the same weight at the same age as your's at 10 months.
.
Like said , if he's active, happy, healthy, and eating well and pooing regularly I wouldn''t worry, your's is just going to be more petit.