How long will baby go on hunger strike?

I have a 5 month old sulcata tortoise and he/she is growing but definitely very small for his age. I got him (don’t know gender obviously but going to call him for simplicity) from a reptile expo and have come to realize he was probably started poorly. He pretty much only wants to eat romaine. For 3 weeks now I have been mixing small cut up pieces of the following: romaine with dry tortoise hay (small sprinklings mixed in), cut fresh wheat grass, dandelion greens and other various leafy greens that are healthier and calcium powder. I’ve been giving a large portion of this salad fresh every single day and after 3 weeks he still will just pick at it and barely touch it. Given his slow growth, I am very determined to get him on a more nutritious food blend than just romaine but at this point his hunger strike is starting to worry me. Will he eventually give in and eat this mix if I continue to stick to it?