Try washing or rubbing the round things off. After that there is still the problem of the interveinal chlorosis (yellow areas). This indicates a soil minerals problem or a problem with minerals in the irrigation water - read on the web about the climate and soil conditions avocado plants require, in order to find out what you might have to do to keep them going there.

Hi

So i just tried rubbing things off with water and vinegar. On my other plants which are olive trees, a lot of shells came out but it became very difficult to clean them. Is there anything I can do to put in the soil to kill them through the plant or something i can spray on them to fix it ? I really don't want all my plants to die

Ill check the soil condition thing

Thank you so much for your help <3

The "shells" if they come off the leaf with rubbing, are scale insects.

Do not add vinegar to the water.

Please post a picture of the entire plant.Likely it's in too small a pot; and/or getting too little water; and/or needs fertilizer

You can also treat scale insects with horticultural oil (summer oil) or neem oil (the former being preferred), just remember to read the label and follow the instructions because if you apply it at too high a temperature you can have problems.

Cheers, Frank