At 7 weeks squirrels should have some type of rodent block in their cage at all times so they can start taking an interest in solid food.
There are two types of rodent block. One type is free feeding, meaning they can have as much of it as they’ll eat. It’s completely balanced and doesn’t require additional veggies in the diet if they are consuming it. Unfortunately this type of block is less palatable so isn’t as readily accepted. Brands of this block are Harlan Teklad (Envigo), Mazuri and Oxbow. The first brand must be purchased online. There are recipes to create boo balls with this type of block which makes it tastier.
The second type of block is a supplemental block which is more readily accepted. Two of these blocks are given daily along with healthy veggies, and an occasional fruit or nut from the healthy diet pyramid in the Squirrel Nutrition section. This brand must also be purchased online at Henry’s Healthy Pets. The picky formula and the hazelnut ones are well liked.
Initially, you only want to offer the block while continuing the formula. Only after the squirrel is eating the block well do you add in any veggies. At this age, I’d never give any nuts. It’s like expecting a toddler to eat spinach after getting a taste of ice cream.