How come whenever I tend to eat clean I get a really dry mouth?

Roughly my diet is...

Meal 1: Scrambled egg on toast or oats

Meal 2: Metrx shake

Meal 3: chicken, vegetables and brown rice

Meal 4: baked potato, tuna and mayo

Meal 5: whey, dextrose (post training)

Meal 6: whey, flax

Any ideas?

The diet works out about 2300 cal's with a 40/30/30 split.