Hi.
Welcome to the forum.
Not a swimmer but here is an extract from a Sports website about the activities you are undertaking ? Someone else may be along shortly who can help you more ?
ANAEROBIC HIGH INTENSITY ACTIVITIES
Predisposition to hyperglycaemia - in other words it raises your Bg levels.
VARIABLES INVOLVING COUNTER-REGULATORY HORMONES
Competition stress, heat stress including high humidity, dehydration, high pre-exercise blood glucose and arm exercises may augment counter-regulatory hormone response to exercise predisposing to hyperglycaemia. (High Bg levels)
As you can see what you are doing doesn't normally decrease your BG levels especially if you were high to start with. Do you know your pre-exercise numbers ?
Muscles/Arms may just be that they are protesting at the workload ? OR Lactic acidosis may occur as a consequence of vigorous or prolonged exercise but is usually of no consequence and self-correcting, unless other pathology such as hyperthermia is present.
It might be that you need a high carb drink to give you the extra glucose for such a punishing workout ? The body always needs a fuel to keep it going and by eating after exercise you may well have literally 'nothing in the tank,' therefore your body will 'Liver Dump' and keep doing so until such time as you provide it with some fuel. The levels will rise all the time.
Have you consulted a Sports Nutritionist/Dietician at all about this ?