Hi Karen,
Thal minors generally report more problems as they get older. I attribute this to the years of oxidation, which is caused by the imbalance in globin chains, the defective red blood cells produced and the ultimate hemolysis or destruction of these RBCs. At all levels of thalassemia, depletion of vitamins and minerals takes place. Your diet alone cannot compensate for this depletion. Your husband may disagree, but he is wrong, just as every doctor who makes the claim that thal minor is asymptomatic is wrong, and this includes most doctors on earth. There is over a 50% chance that your husband is deficient is vitamin D. Perhaps testing might open his eyes a bit. I would suggest that you and your daughter both get the vitamin D test. Over half the people on earth are thought to be deficient, and thal only makes this more likely. If your levels are not at least a minimum of 35, correction will be needed. My own level could not be corrected until I took 5000 IU daily and I make a point of getting a lot of sun during the warm months.
In addition to vitamin D if needed, I suggest natural vitamin E complex, B-Complex, folic acid, vitamin C and magnesium. All are needed for building and maintaining the health of RBCs. At your age, L-carnitine or L-arginine should also be considered, as they help to increase the nitric oxide, NO levels in the body. NO is depleted by oxidation and is a big factor in loss of flexibility of blood vessels as aging takes place. None are expensive vitamins. I have taken the antioxidant, natural vitamin E for 37 years and absolutely swear by it. You will not see overnight results with supplements, as this requires long term dedication. Keep in mind that thal minors have a lower oxygen supply because their hemoglobin level is lower, so endurance exercise will be a struggle. Proper nutrition, staying well hydrated and learning proper breathing techniques are all keys to optimizing your endurance. Recognizing when fatigue means "enough, it's time to rest" is also very important. Many minors find that a short afternoon nap helps them get through the rest of the day. In terms of diet and nutrition, think antioxidants. These are essential in the battle against the damage that thalassemia does to the body. I find that thals have no room for error, so junk foods and empty calories should be avoided. Fruits, raw vegetables, nuts and beans are all good sources of antioxidants. Avoid sugars and processed foods as much as possible.
By the way, Pete Sampras would not reveal his thal minor when he was actively competing. His strategy was to dispatch opponents as quickly as possible, so enduring long matches could be avoided. He admitted to this once he retired. Even the great one understood that his energy supply was limited. Revealing it would give opponents an edge, so he waited until retirement to acknowledge this.