Yes highlighting and heat styling can damage the curl pattern, temporarily or permanently. Work with your hair properties, if your hair is fine or damaged use hydrolysed protein, if it's porous or lacking in elasticity use coconut oil. Also beneficial for damaged hair includes ceramides, 18-MEA and panthenol.

I find my underlayers suffer from drying out too quickly when plopping too.
2a-2c, medium texture, porous/ colour treated. Three years CG. Past bra strap length heading for waist.

CO-wash: Inecto coconut/ Elvive Volume Collagen
Treatments: Komaza Care Matani, coconut/ sweet almond oils, Hairveda Sitrinillah
Leave in: Fructis Sleek & Shine (old), Gliss Ultimate Volume, various Elvive
Styler: Umberto Giannini jelly, Boots Essentials gel
Flour sack towel, pixie diffuse or air dry.
Experimenting with: benign neglect