Brief Answer:
certainly possible.

Detailed Answer:
There are several ways in which marijuana may cause this. First, there is the direct irritation. The quality control of the cigarettes is not reliable and there could be direct contact of a lit end with the mouth. It is well-known that intoxicated subjects do not reliably notice this.
Spray marijuana seems oddly enough EVEN MORE risky of mouth irritation.
http://www.ncbi.nlm.nih.gov/pubmed/0000

Then, people can have allergies to marijuana. Although benadryl might lower the symptoms, it's a really strong reason to never have anything to do with it again as the allergic symptoms can easily be worse the next time and can cause fatal locking up of the airways.

ANd.... it often (perhaps MOST often) isn't the marijuana. Several epidemics of dozens or more people have had this when the marijuana is "tainted". You can google "tainted marijuana" or "paraquot" and see for yourself.

The legalized marijuana is not tainted. Testing it WITH SUPERVISION and benadryl and emergency 911 phoning available is pretty safe.

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Brief Answer:
Can only give general info

Detailed Answer:
and... while you can have a yeast infection that can do this (which not only can and should be easily treated but also implies something else going on like diabetes or an immune problem).
an allergic reaction to something in the mouth seems possible. I can be a food that you often eat... but if it has been continuously present for months, it has to be something you have in your mouth a lot of the time. And marijuana while it is rare to do this, is a foreign and often irritating substance. Additives onto marijuana Frequently do this.
Benadryl (diphenhydramine) often helps allergies. Specific medicines are needed for yeast infections.
I cannot do definite diagnoses without seeing it and I cannot prescribe to someone not my patient.

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