sores are having multiuple reasons behind it, most often cited are, Vitamin B12
, Streptococcal bacterial infections, Autoimmune/ allergic reactions, and Iron defecienceis. As per of current knwoledge, it has almost non significnat association with orange juices. Orange Juices may at maximum lead to dental Erosion causing senstivity. Instead from your case history of Enlarged adenoids and Tonsils along with canker sores, it more of look like a STREPTOCOCCAL infection
It can be well treated by,
a) gargle with warm water mixed with one capsule of RESTICIlLLIN-250mg (Tetracycline
b) Take Vit. B Complex Caps at night with Milk (For Iron/ Vit B defeciency correction)
c) Apply Dologel CT on affected sores
d) Maintain Good Oral Hygeine (Brush twice and use mouthwashes)
and Lastly as you are already taking Amox, things should go better within 2/ 3 days.